Patent Application
20070248477
The present invention relates generally to peristaltic pumps and more specifically to fluidic cassettes used in ophthalmic surgical equipment.
Most prior art peristaltic pumps work by compressing or squeezing a length of flexible tubing (sometimes between a fixed race) using a rotating roller head. As the roller head rotates, the rollers pinch off a portion of the tubing and push any fluid trapped in the tubing between the rollers in the direction of rotation. Peristaltic pumps are widely used in medical applications because of their predictable, constant flow properties. These prior art systems, however, typically require manual connection of the pump tube segment around the rotating roller head.
Prior art peristaltic pumps using rotating roller heads also typically impart unwanted pressure pulsations. Several pulsation damping devices have been developed to address this problem (see e.g., U.S. Pat. No. 4,921,477 (Davis)).
Another prior art pump is disclosed in U.S. Pat. No. 6,293,926 B1 (Sorensen, et al.) describes a peristaltic pump having a molded flow channel contained on an elastomeric sheet that is bonded or mechanically attached to a rigid substrate. The pump head rollers are mounted radially from the axis of rotation of the pump motor and compress the elastomeric flow channels against the rigid substrate. The commercial embodiment of the invention described in this patent is sold as the INFINITI® Vision System by Alcon Laboratories, Inc., Fort Worth, Tex. This surgical console uses a Fluid Management System or cassette wherein the elastomeric sheet is friction fit into the rigid substrate without the use of any adhesives Such a construction method has proven to be extremely reliable, but this commercial system is intended primarily for cataract surgery and has no other source of vacuum other than the peristaltic pump. Therefore, the fluidic system is exposed primarily to negative pressure or vacuum and is not exposed to transient high positive pressures, such as are encountered during a reflux operation in posterior segment surgical procedures using a venturi pump as the primary source of vacuum. These high positive pressures can be as high as 700 mm Hg and have the potential to cause failure at the elastomer/substrate interface if a friction fit construction technique is used.
Accordingly, a need continues to exist for a surgical cassette that reduces the potential for cassette failure under transient positive pressures.
The present invention improves upon prior art cassettes by providing a cassette having a molded flow channel contained on an elastomeric sheet that is bonded or mechanically attached to a rigid substrate. A surgical console contains a cassette receiving area having a pump head with rollers that are mounted radially from the axis of rotation of the pump motor and compress the elastomeric flow channels against the rigid substrate. The cassette is held in place against the pump head by a latching mechanism that draws the cassette against the pump head. The elastomeric sheet contains a raised ridge or boss integrally formed as part of the elastomeric sheet at or near the area(s) of the elastomeric sheet that is/are subject to high transient or static pressures. The ridge allows the elastomeric sheet to be firmly pressed against the cassette receiving portion of the surgical console, yet still allow the cassette to be drawn against the pump head. The firm engagement of the sheet ridge against the cassette receiving portion of the surgical console helps to ensure that the elastomeric sheet does not become dislodged when the cassette is exposed to high transient pressures.
One objective of the present invention is to provide a peristaltic pump that uses molded elastomeric flow channels.
Another objective of the present invention is to provide a peristaltic pump having radially oriented pump rollers.
Yet another objective of the present invention is to provide a peristaltic pump having pump rollers that compress elastomeric flow channels against a rigid substrate.
Still another objective of the present invention is to provide a cassette having an elastomeric sheet fitting to a rigid substrate.
Still another objective of the present invention is to provide a cassette having an elastomeric sheet fitting to a rigid substrate so that the elastomeric sheet does not become dislodged when the cassette is exposed to high transient pressures.
These and other advantages and objectives of the present invention will become apparent from the detailed description, drawings and claims that follow.
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This description is given for purposes of illustration and explanation. It will be apparent to those skilled in the relevant art that modifications may be made to the invention as herein described without departing from its scope or spirit.
